MEASURING THE SENSITIVITY OF AN INDIRECT PREDATOR GUT CONTENT ELISA: DETECTABILITY OF PREY REMAINS IN RELATION TO PREDATOR SPECIES, TEMPERATURE,TIME AND MEAL SIZE.

Authors: Hagler, James; Naranjo, Steven

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Predaceous insects, those that feed on other insects, are thought to play an important role in decreasing pest populations. However, due to the small size and elusive behavior of predators and pests, it is difficult to measure predation in the field by direct observation. We have developed tests, similar to those used in medicine to screen urine for drug residues and test for pregnancy at home, which enable us to precisely, rapidly, and economically analyze the stomach contents of predatory insects. These tests are called gut content enzyme linked immunosorbent assays (ELISAs). In this study we identified some variables that can affect the outcome of a gut content ELISA. Specifically, we examined what effect time since feeding, temperature since feeding, and meal size have on the outcome of an ELISA on three species of predators. The sensitivity and efficacy of the ELISA was dependent on the predator species examined. Small predators were emore immunoresponsive to the ELISA than large predators. Furthermore, the assay sensitivity was dependent on the number of prey consumed, on the elapsed time after feeding, and on the temperature at which the predators were held. Results from this experiment will help us to standardize gut content immunoassays thereby leading to a more precise evaluation of predaceous natural enemies.

Technical Abstract: The gut contents of three species of insect predators that were either fed variable amounts of pink bollworm eggs or a fixed amount of eggs but held at variable time and temperature regimes were assayed by an indirect enzyme-linked immunosorbent assay (ELISA). The sensitivity and efficacy of the ELISA was dependent on the predator species examined. Small predators were more immunoresponsive to the ELISA than large predators. Furthermore the assay sensitivity was dependent on the number of prey consumed, on the elapsed time after feeding, and on the temperature at which the predators were held. The smaller predator species retained recognizable traces of prey remains for longer periods than larger predator species. The ELISA efficacy decreased with increasing ambient temperatures. A series of regression equations have been developed to estimate the mean detection interval of prey in a predator's gut that takes into account the predator species examined, the amount of the prey consumed, and the ambient, after- meal temperature.